Currently, in the fields of information science, medical engineering applications, and welfare device control by brain activity, operation of a device is mainly performed through an input operation of various switches, a joystick, a mouse and the like by hand. Meanwhile, in the field of nursing care/welfare device development, a need is felt for a device that can be operated by other parts of the body for operators with physically disabled hands or legs.
Conventionally, speech assisting devices using a character board or picture cards are known. Technologies related to devices for assisting the conversation of users with disabilities in language function or hearing are discussed in Patent Documents 1 and 2, for example. Patent Document 1 describes a technology such that the letters of the 50 Japanese syllabary on a character board are sequentially lighted on a block by block basis and selected, and a technology involving the use of a message board for selecting a request for bodily care. Patent Document 2 describes a communication assist system for selecting a symbol display by using a portable information terminal. However, in the field of nursing care/welfare device development, a device that enables the direct transmission of an intention without requiring the conventional operations is desired for operators who cannot perform complex input operations, such as the elderly or the sick. There is also a need for a device for patients with speech impediment or the elderly that enables the transmission of an intention regarding basic personal nursing care or feelings, to the helper in a simpler manner.
The progress in brain science in recent years has led to various studies on the relationship between human thought and behavior and brain activity. Attention is being focused on Brain-Machine Interface (BMI) technology for controlling an external device or conveying an intention to others by noting a biosignal, such as brain activity.
For example, neuromarketing is the study for investigating the brain activity related to consumer behavior by using a functional MRI (fMRI) device and the like. A study is known in which, through a brain activity measurement experiment using a fMRI apparatus, brain regions associated with preferences or brand awareness for Coca cola and Pepsi cola were identified and brain activity differences were investigated (Non-patent Document 1).
The present inventors have shown, through a measurement technique involving extracellular recording of the action potential of a single neuron by electrodes disposed in an animal brain, and by a neuronal ensemble activity simulation, that the representation of relationships among a plurality of external stimuli (experimental conditions) in the brain can be estimated in terms of low-dimensional spatial information (see Non-patent Document 2). However, many aspects of brain activity are still unknown, and the measurement methods have restrictions.
The present inventors have also proposed a virtual decision function and shown a calculation method therefor (see Non-patent Document 3). Non-patent Document 3 describes a method for predicting an alternative behavior from a single neuron activity as an example of neural activity.
Patent Document 1: JP-A-2004-286768
Patent Document 2: JP-A-2003-255825
Non-patent Document 1: McClure S M, et al., “Neural Correlates of Behavioral Preference for Culturally Familiar Drinks” Neuron 44, p 379-387, 2004
Non-patent Document 2: N. Matsumoto and R. Hasegawa, “Prediction of Multidimensional Decision-making Based on Single Trial of Frontal Association Area Neuronal Ensemble”, Neuroscience Research, Vol. 58, Supplement 1, page S161 (P2-f34), 2007
Non-patent Document 3: R. Hasegawa et al., “Single trial-based prediction of a go/no-go decision in monkey superior colliculus”, Neural Networks 19(2006) 1223-1232
There is a need for a device such that an intention can be conveyed to industrial or entertainment devices such as a robot and a wireless control device, or welfare devices such as an electric wheelchair and an electronic character board, without using hands or legs and by as simple an operation as possible. However, the various latest input apparatuses that have been researched and developed for the above purposes require their own unique input systems or input apparatuses. Thus, the various input apparatuses need to be purchased, and it takes time to learn how to operate them.
The technology that examines brain activity by using a functional MRI (fMRI) apparatus and the like requires measurement within the MRI apparatus, so that a real-time input operation cannot be performed and a large-size apparatus is required.
The apparatuses that have been proposed by conventional researches on communication have too much noise for the measurement of biological information such as brain waves, resulting in a low probability of correct answers and a long time before a determination can be made.
The core of the above conventional BMI technologies should be the technology for real-time decoding of an intention decision in the brain. However, it is extremely difficult to decode an intention decision in the brain accurately and quickly under the condition of the on-scalp brain wave recording with poor S/N ratio, or the neuron activity recording with a small number of simultaneously recordable signals. For example, according to a technique, a plurality of alternative visual stimuli is presented on a personal computer screen, and the alternative selected by an operator is predicted or inferred on the basis of the intensity of response of an induced brain wave (an event-related brain wave referred to as “P300”, such as a positive potential change 300 milliseconds after the presentation of stimulus) obtained when the stimuli are flashed (lighted) in a pseudo-random manner. In this case, there has been the problem that increasing the number of presentations may increase prediction accuracy but results in longer time, and, conversely, decreasing the number of presentations leads to a decrease in accuracy although the time required for prediction can be decreased.
The present invention aims to overcome the above problems and an object of the present invention is to discriminate an intention in the brain without erroneous identification and in a short time. Another object of the present invention is to enable a device to be directly operated in real-time according to a thought in the brain of an operator. Another object is to provide an apparatus and method such that a patient with speech impediment or the elderly can convey intentions regarding basic personal nursing care or feelings directly and more simply to the helper.